Method for precipitation of polyphenylene ether

ABSTRACT

An object of the present invention is to provide a method for precipitating polyphenylene ether which decreases the number of fine particles thereof and reduces periodic fluctuations in particle size, thereby being able to stably produce homogeneous polyphenylene ether particles. The invention relates to a method for precipitating polyphenylene ether by mixing a polyphenylene ether solution comprising polyphenylene ether and a good solvent therefor with a poor solvent for polyphenylene ether to precipitate polyphenylene ether particles, the method comprising: using a precipitation tank equipped with (a) a draft tube, (b) an at least one-stage stirring blade disposed in the draft tube and selected from an inclined paddle blade, a screw blade and a ribbon blade, (c) one or more baffles disposed on the outside of the draft tube, (d) a solution supply port, (e) a poor solvent supply port and (f) an exhaust port; adding, to a mixed solution comprising the good solvent, the poor solvent and polyphenylene ether particles and circularly flowing by rotation of the stirring blade (b), the polyphenylene ether solution from the solution supply port (d) and concurrently a poor solvent from the poor solvent supply port (e), thereby precipitating polyphenylene ether particles; and discharging and recovering the precipitated polyphenylene ether particles together with the mixed solution from the exhaust port (f).

TECHNICAL FIELD

The present invention relates to a method for precipitatingpolyphenylene ether, and a method for precipitating polyphenylene etherwhich decreases the number of fine particles of polyphenylene etherparticles and reduces periodic fluctuations in particle size, therebybeing able to stably produce homogeneous polyphenylene ether particles.

BACKGROUND ART

A polyphenylene ether resin made from polyphenylene ether is a plasticmaterial which can provide products and parts in desired form by amolding process such as melt injection molding or melt extrusionmolding, and which has been widely used as a material for products andparts in the field of electronics and electricity, the field ofautomobiles and the field of various other industrial materials.

As a method for producing polyphenylene ether, there is a method ofoxidatively polymerizing a phenol compound in the presence of a coppercompound and an amine compound in a good solvent for polyphenyleneether. As a method for precipitating the polyphenylene ether from apolyphenylene ether solution obtained by this method, there is known amethod for precipitating polyphenylene ether particles by adding a poorsolvent for polyphenylene ether, such as methanol, to the solution.

However, the polyphenylene ether particles precipitated by conventionalmethods contain a lot of fine particles therein, and have the problem ofclogging in a filtering step required after a sedimentation step in apolyphenylene ether production process and also the problem that apolyphenylene ether composition is not smoothly supplied to an extruderin a melt kneading step required when being pelletized.

Further, in the polyphenylene ether particles precipitated byconventional methods, the phenomenon of periodic fluctuations inparticle size thereof occurs, which poses the problem that theproductivity fluctuates in the filtering step and drying step.

Accordingly, the conventional polyphenylene ether production methodssuffer from the problem with respect to productivity in other steps inthe polyphenylene ether production process and in the step for obtainingpellets of the polyphenylene ether composition, so that they do notsufficiently comply with industrial demands.

An object of the invention is to provide a method for precipitatingpolyphenylene ether by mixing a polyphenylene ether solution with a poorsolvent for polyphenylene ether to precipitate polyphenylene etherparticles, which can stably produce polyphenylene ether particles withfewer fine particles of the polyphenylene ether particles, reducedperiodic fluctuations in particle size, and with homogeneous particlesize, thus sufficiently complying with the industrial demands.

DISCLOSURE OF THE INVENTION

As a result of extensive studies for achieving the above-mentionedobject, the present inventors have completed a method for precipitatingpolyphenylene ether by mixing a polyphenylene ether solution comprisingpolyphenylene ether and a good solvent therefor with a poor solvent forpolyphenylene ether to precipitate polyphenylene ether particles,wherein the number of fine particles of the polyphenylene etherparticles is decreased, and periodic fluctuations in particle size arereduced, thereby making it possible to stably produce homogeneouspolyphenylene ether particles and sufficiently complying with theindustrial demands.

That is, the invention provides a method for precipitating polyphenyleneether by mixing a polyphenylene ether solution comprising polyphenyleneether and a good solvent therefor with a poor solvent for polyphenyleneether to precipitate polyphenylene ether particles, the methodcomprising:

using a precipitation tank equipped with (a) a draft tube, (b) an atleast one-stage stirring blade disposed in the draft tube and selectedfrom an inclined paddle blade, a screw blade and a ribbon blade, (c) oneor more baffles disposed on the outside of the draft tube, (d) asolution supply port, (e) a poor solvent supply port and (f) an exhaustport;

adding, to a mixed solution comprising the good solvent, the poorsolvent and the polyphenylene ether particles, the mixed solutioncircularly flowing by rotation of the stirring blade (b), thepolyphenylene ether solution from the solution supply port (d) andconcurrently adding a poor solvent from the poor solvent supply port(e), thereby precipitating polyphenylene ether particles; and

discharging and recovering the precipitated polyphenylene etherparticles together with the mixed solution from the exhaust port (f).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view showing the precipitation tank used inExample 1; and

FIG. 2 is a schematic plan view showing the baffles disposed on theoutside of the draft tube of the precipitation tank used in Example 1.

In the drawings, the reference character (a) designates a draft tube,(b) designates a stirring blade (one-stage paddle), (c) designates abaffle, (d) designates a solution supply port, (e) designates a poorsolvent supply port, (f) designates an exhaust port, D designates thediameter of the precipitation tank, H designates the liquid height, DHdesignates the height of the draft tube, and SD designates the diameterof the blade.

BEST MODE FOR CARRYING OUT THE INVENTION

The polyphenylene ether of the invention has a main chain structure ofthe following formula (1):

R₁ and R₄ in the polyphenylene ether of the invention represented byformula (1) each independently represent hydrogen, primary or secondarylower alkyl, phenyl, aminoalkyl or hydrocarbonoxy. R₂ and R₃ eachindependently represent hydrogen, primary or secondary lower alkyl orphenyl.

The polyphenylene ether of the invention is a polymer or a copolymerhaving a reduced viscosity measured with a 0.5 g/dl chloroform solutionat 30° C. of within the range of 0.15 to 1.0 dl/g, and more preferablywithin the range of 0.20 to 0.70 dl/g.

Specifically, the polyphenylene ether of the invention ispoly(2,6-dimethyl-1,4-phenylene ether),poly(2-methyl-6-ethyl-1,4-phenylene ether),poly(2-methyl-6-phenyl-1,4-phenylene ether),poly(2,6-dichloro-1,4-phenylene ether) or the like.

Other specific examples of the polyphenylene ethers of the inventionalso include a polyphenylene ether copolymer such as a copolymer of2,6-dimethylphenol and a phenol (e.g., 2,3,6-trimethylphenol or2-methyl-6-butylphenol).

Of the polyphenylene ethers of the invention described above,poly(2,6-dimethyl-1,4-phenylene ether) and a copolymer of2,6-dimethylphenol and 2,3,6-trimethylphenol can be preferably used, andmost preferred is poly(2,6-dimethyl-1,4-phenylene ether).

There is no particular limitation on the polymerization method of thepolyphenylene ether for use in the invention.

Examples of the polymerization method of the polyphenylene ether for usein the invention include the method described in U.S. Pat. No.3,306,874, in which 2,6-xylenol is oxidatively polymerized using acomplex of a cuprous salt and an amine as a catalyst. The methodsdescribed in U.S. Pat. Nos. 3,306,875, 3,257,357 and 3,257,358, JP52-017880 B, JP 50-051187 A, JP 63-152628 A and the like are alsopreferred as the production methods of the polyphenylene ether.

The end structure of the polyphenylene ether of the invention ispreferably a structure of the following formula (2):

wherein R₁, R₂, R3 and R₄ are each defined in the same manner as withR₁, R₂, R₃ and R₄ in the above-shown formula (1).

The end structure of the polyphenylene ether of the invention is morepreferably a structure of the following formula (3):

wherein R₅ and R₅′ each represent hydrogen or an alkyl group.

Techniques for obtaining the polyphenylene ether having an end structureof formula (3) include, for example, a method of oxidatively coupling2,6-dimethylphenol in the presence of a primary or secondary amine usinga catalyst containing copper or manganese.

As the above-mentioned primary or secondary amine, a dialkylamine ispreferred, and di-n-butylamine, dimethylamine or diethylamine is morepreferably used.

The good solvent for the polyphenylene ether of the invention means asolvent which satisfactorily dissolves polyphenylene ether to form ahomogeneous polyphenylene ether solution.

The polyphenylene ether solution of the invention is a solution in whichpolyphenylene ether is homogeneously dissolved in the good solvent.

The polyphenylene ether concentration in the polyphenylene ethersolution of the invention is preferably from 10 to 30% by weight basedon the polyphenylene ether solution.

As the good solvent for the polyphenylene ether of the invention,preferred is at least one solvent selected from benzene, toluene andxylene.

The poor solvent for the polyphenylene ether of the invention is asolvent which does not dissolve polyphenylene ether.

As the poor solvent for the polyphenylene ether of the invention,preferred is at least one solvent selected from methanol, ethanol,isopropanol, n-butanol, acetone, methyl ethyl ketone and water.

In the invention, it is preferred that the good solvent forpolyphenylene ether comprises at least one solvent selected frombenzene, toluene and xylene, and the poor solvent for polyphenyleneether comprises at least one solvent selected from methanol, ethanol,isopropanol, n-butanol, acetone, methyl ethyl ketone and water.

In the invention, it is most preferred to use toluene as the goodsolvent for polyphenylene ether, and methanol as the poor solvent forpolyphenylene ether.

The polyphenylene ether particles of the invention are particlescomprising polyphenylene ether.

The polyphenylene ether particles of the invention are mainly intendedfor use in the formation of a composition with other components by meltkneading after filtering and a drying step. As the polyphenylene etherparticles of the invention, it is preferred that the average particlesize is 400 μm or more, and that the content of fine particles having aparticle size of 105 μm or less is 5% by weight or less.

As the polyphenylene ether particles, it is more preferred that theaverage particle size is 450 μm or more, that the fluctuation inparticle size during precipitation, that is, the fluctuation in averageparticle size over precipitating time, is 100 μm or less, and that thecontent of fine particles having a particle size of 105 μm or less is 2%by weight or less.

As the polyphenylene ether particles, it is especially preferred thatthe average particle size is 500 μm or more, that the fluctuation inparticle size during precipitation, that is, the fluctuation in averageparticle size over precipitating time, is 50 μm or less, and that thecontent of fine particles having a particle size of 105 μm or less is 1%by weight or less.

In the invention, means for obtaining polyphenylene ether particles havebeen studied. As a result, it has been discovered that the use of aspecific precipitation tank equipped with a draft tube described belowallows the polyphenylene ether solution supplied to be effectively mixedwith the poor solvent to stably precipitate polyphenylene etherparticles, and that discharging a mixed solution in the precipitationtank makes it possible to effectively produce polyphenylene etherparticles with less number of fine particles, reduced periodicfluctuations in particle size, and homogeneous particle size.

Further, the precipitation tank of the invention is a precipitation tankhaving an at least one-stage stirring blade (b) disposed in a draft tube(a) and selected from an inclined paddle blade, a screw blade and aribbon blade, and one or more baffles (c) disposed on the outside of thedraft tube (a).

The draft tube (a) of the invention is a partition wall provided in theprecipitation tank. The shape thereof is most preferably cylindrical.However, the cross section thereof is not limited to circular, but maybe elliptical, polygonal, or the like.

The draft tube (a) of the invention is preferably disposedconcentrically within the precipitation tank.

The inclined paddle blade of the invention is preferably a stirringblade formed by inclining an ordinary paddle at 5 to 85 degrees withrespect to the rotational direction, and more preferably a stirringblade formed by inclining an ordinary paddle at 35 to 55 degrees. When apaddle blade having no inclination is used, the circulation flowdescribed below is not formed, so that the mixed solution does notbecome homogeneous, resulting in increased fluctuations in the averageparticle size of the polyphenylene ether particles.

The screw blade of the invention is preferably a stirring blade having ashape similar to that of a screw used for ships.

The ribbon blade of the invention is preferably a helical stirring bladeof single blade type or double blade type.

The baffles (c) of the invention are baffle plates fixed in a stirringtank in order to control the flow.

In the precipitation tank of the invention, the mixed solutioncomprising the good solvent, the poor solvent and polyphenylene etherparticles is pushed out to the bottom of the tank or the liquid level ofthe mixed solution while circulating in the draft tube with the rotationof the stirring blade, and then, flows between the draft tube and a wallof the precipitation tank as an approximately perpendicular ascendingflow or descending flow to circularly flow inside and outside the drafttube.

In the precipitation tank of the invention, the circulation direction ofthe mixed solution depends on the rotational direction of the stirringblade and the shape of the stirring blade.

In the invention, the polyphenylene ether solution is added from asolution supply port (d) to the mixed solution.

In the invention, the polyphenylene ether solution is preferably addedto the mixed solution from the solution supply port (d) provided abovethe liquid level of the mixed solution.

In the invention, a method of adding dropwise the polyphenylene ethersolution from the solution supply port (d) provided above the liquidlevel of the mixed solution to a downward-flowing portion of thecircularly flowing mixed solution can be more preferably used, becausethis causes no occurrence of scale of the polyphenylene ether in theprecipitation tank.

In the invention, the poor solvent is added from a poor solvent supplyport (e) at the same time that the polyphenylene ether solution is addedfrom the solution supply port (d) to the mixed solution.

The poor solvent supply port (e) is preferably provided directly on thewall of the precipitation tank above the liquid level of the mixedsolution or between the draft tube and the precipitation tank above theliquid level of the mixed solution.

In the precipitation method of the polyphenylene ether of the invention,the polyphenylene ether particles precipitated are discharged togetherwith the mixed solution from an exhaust port (f), and recovered.

In the precipitation method of the polyphenylene ether of the invention,the mixed solution is preferably overflowed from the exhaust port (f)provided at the position of the liquid level of the mixed solution inthe precipitation tank, thereby discharging and recovering thepolyphenylene ether particles from the precipitation tank.

In the precipitation method of polyphenylene ether of the invention, itis preferred that the ratio of the precipitation tank diameter/theliquid height of the mixed solution in the precipitation tank (that is,the distance from the liquid level to the bottom of the tank) is from0.1 to 2, that the ratio of the height of the draft tube/theabove-mentioned liquid height is from 0.05 to 0.6, and that the ratio of“the vertical interval between the liquid level and the most upperportion of the draft tube”/the above-mentioned liquid height is from0.01 to 0.3.

When the liquid level is at a position higher than the most upperportion of the draft tube, “the vertical interval between the liquidlevel and the most upper portion of the draft tube” as used herein shallbe considered to be a positive value, and when the liquid level is lowerthan the most upper portion of the draft tube, it shall be considered tobe a negative value.

When the ratio of the precipitation tank diameter/the liquid height ofthe mixed solution in the precipitation tank (that is, the distance fromthe liquid level to the bottom of the tank) is less than 0.1, it isunfavorable in terms of productivity.

When the ratio of the precipitation tank diameter/the liquid height ofthe mixed solution in the precipitation tank (that is, the distance fromthe liquid level to the bottom of the tank) exceeds 2, high stirringpower is required, which is unfavorable in terms of production cost.

In the precipitation method of the polyphenylene ether of the invention,it is preferred to carry out stirring with such stirring power that themixed solution can be effectively discharged from the exhaust port (f),and that the polyphenylene ether particles do not stay on the bottom ofthe precipitation tank.

When the ratio of the draft tube height/the above-mentioned liquidheight is less than 0.05, a stable ascending flow or descending flow maybe not obtained in some cases.

When the ratio of the draft tube height/the above-mentioned liquidheight exceeds 0.6, an ascending flow or descending flow may be notobtained stably in some cases.

When the ratio of “the vertical interval between the liquid level andthe most upper portion of the draft tube”/the above-mentioned liquidheight is less than 0.01, the discharge of the mixed solution may be notstabilized in some cases.

When the ratio of “the vertical interval between the liquid level andthe most upper portion of the draft tube”/the above-mentioned liquidheight exceeds 0.3, a stable ascending flow or descending flow may benot obtained in some cases.

In the precipitation method of polyphenylene ether of the invention, theweight ratio of the poor solvent/the good solvent in the mixed solutionis preferably from 0.3 to 2.0.

When the weight ratio of the poor solvent/the good solvent in the mixedsolution is less than 0.3, there is high possibility that scale willoccur during precipitation.

When the weight ratio of the poor solvent/the good solvent in the mixedsolution exceeds 2.0, it is unfavorable in terms of production cost.

In the precipitation method of polyphenylene ether of the invention, itis more preferred that water contained in the poor solvent is from 0.3to 50 parts by weight.

In the precipitation method of polyphenylene ether of the invention, thetemperature of the mixed solution is preferably from 30 to 60° C.

In the precipitation method of polyphenylene ether of the invention, thequotient obtained by dividing the sum of the supply speed of thepolyphenylene ether solution supplied from the supply port into theprecipitation tank and the supply speed of the poor solvent concurrentlysupplied into the precipitation tank by the liquid amount of the mixedsolution remaining in the precipitation tank is defined as the averageresidence time during which the polyphenylene ether particles stay inthe precipitation tank.

In the invention, the average residence time during which thepolyphenylene ether particles stay in the precipitation tank ispreferably from 2.0 to 30 minutes.

When the average residence time is 2.0 minutes or less, the content ofthe good solvent in the polyphenylene ether particles is increased,which may sometimes cause the particles to be firmly fixed to oneanother after discharge.

When the average residence time exceeds 30 minutes, it poses a problemin terms of productivity and production cost.

The precipitation method of polyphenylene ether of the invention canstably produce homogeneous polyphenylene ether particles with anextremely less number of fine particles thereof and extremely reducedperiodic fluctuations in polyphenylene ether particle size, so that itconstitutes a precipitation method of polyphenylene ether which compliessufficiently with the industrial demands.

The polyphenylene ether particles obtained by the precipitation methodof polyphenylene ether of the invention are homogeneous polyphenyleneether particles with extremely less number of fine particles thereof andextremely narrow particle size distribution, so that they give extremelyhigh productivity when melt kneaded with another composition.

That is, the polyphenylene ether particles obtained by the precipitationmethod of polyphenylene ether of the invention can be preferably used asa raw material for a polyphenylene ether composition.

The polyphenylene ether particles of the invention can be extremelypreferably used in a polymer alloy obtained by kneading with athermoplastic resin such as a styrenic resin, a polyamide, a polyimide,a polyetherimide, a polyester or a polycarbonate.

The polyphenylene ether particles of the invention, and thepolyphenylene ether composition and polymer alloy using thepolyphenylene ether particles of the invention are not particularlylimited in their applications, and are widely applicable to applicationsin the field of electronics and electricity, the field of automobilesand the fields of various other industrial materials.

The polymer alloy or polymer composite containing the polyphenyleneether particles of the invention is preferably applicable in the fieldof electronics and electricity, the field of automobiles and the fieldof various other industrial materials.

Further, the polyphenylene ether particles obtained by the precipitationmethod of polyphenylene ether of the invention are homogeneouspolyphenylene ether particles having a greatly smaller number of fineparticles and extremely narrow particle size distribution, so thatproductivity is stabilized in the filtering step and the drying step.

EXAMPLES

Embodiments of the invention will be illustrated in greater detail withreference to the following examples, but the invention should not beconstrued as being limited thereto.

In the Examples and Comparative Example, the following polyphenyleneethers were used.

A-1: According to the method described in Example 3 of JP 59-023332 B,13% by weight of a toluene solution of 2,6-dimethylphenol was added inthe presence of each catalyst and di-n-butylamine over a period of 35minutes while supplying oxygen, and after 100 minutes lapse of time, thesupply of oxygen was stopped. An aqueous solution of trisodiumethylenediaminetetraacetate was added to the polymerization mixture, andthe mixture was maintained at 70° C. Then, the mixture was sent to acentrifuge manufactured by Sharpless Co., and an aqueous phasecontaining each catalyst and trisodium ethylenediaminetetraacetate wasseparated to obtain a polyphenylene ether solution (A-1) having apolyphenylene ether content of 13.5% and a specific gravity of 0.894.The reduced viscosity of the polyphenylene ether contained in (A-1) was0.53 dl/g, when measured with a 0.5 g/dl chloroform solution.

A-2: A polyphenylene ether solution (A-2) having a polyphenylene ethercontent of 22.3% and a specific gravity of 0.911 was obtained in thesame manner as with the above-mentioned (A-1) with the exceptions that22% by weight of a toluene solution of 2,6-dimethylphenol was used andthe supply of oxygen was stopped after 85 minutes lapse from the startof polymerization. The reduced viscosity of the polyphenylene ethercontained in (A-2) was 0.40 dl/g, when measured with a 0.5 g/dlchloroform solution.

Example 1

A precipitation tank with a jacket, which had an internal diameter of133 mm and was provided with an exhaust port having a bore diameter of25 mm at a position where the vertical interval between the liquid levelfrom the bottom of the tank and the bottom of the tank corresponded to95 mm, was equipped with a draft tube having an internal diameter of 80mm and a draft tube height of 40 mm at a position where the verticalinterval between the liquid level and the most upper portion of thedraft tube corresponded to 27 mm. This precipitation tank was equippedwith a one-stage four-blade inclined paddle blade (inclination: 45degrees, blade diameter: 33 mm) as a stirring blade. The volume of asolution remaining in this precipitation tank was 1100 ml.

In the precipitation tank, 370 g of toluene, 420 g of methanol and 10 gof water were placed, and stirred at a stirring revolution of 600 rpm.By stirring, a spiral descending flow occurred inside the draft tube,and an approximately perpendicular ascending flow occurred between theoutside of the draft tube and an inner wall of the precipitation tank.

Hot water was allowed to flow in the jacket to adjust the temperature inthe precipitation tank to 50° C.

Then, the polyphenylene ether solution (A-1) was added at an additionrate of 190 g/minute at a diagonal position to the exhaust port insidethe draft tube in the precipitation tank, and a mixed solution of 97.5wt % of methanol and 2.5 wt % of water was added at an addition rate of100 g/minute at a diagonal position to the exhaust port and from thesame height outside the draft tube in the precipitation tank. A mixedsolution overflowed from the exhaust port was recovered. In addition,samples were separately collected after 10, 20, 40, 80 and 160 minutesfrom the start of the addition of the mixed solution of methanol andwater. During the precipitation, no change was observed in the flowstate of the mixed solution, and it was stable. The average residencetime was 3.2 minutes.

A sample collected from the recovered mixed solution and the samplescollected after the respective elapses of time were each filtered,washed by mixing methanol, and then, filtered again, followed by vacuumdrying at 140° C. for 4 hours to obtain polyphenylene ether particles.

The mixed solution could be filtered without problems.

The volatile matter content of the dried polyphenylene ether particleswas 0.1% by weight or less.

The resulting polyphenylene ether particles were sieved, and the weightof each fraction was measured.

From a cumulative curve of particle size distribution, the particle sizecorresponding to a center cumulative value (median diameter) was takenas the average particle size.

Similarly, the content (wt %) of particles having a size of 105 μm orless obtained from the cumulative curve of particle size distributionwas taken as the fine particle rate.

Variations with time of the average particle size and the fine particlerate of the resulting polyphenylene ether particles were extremelysmall, and the fine particle rate thereof was extremely low.

When the resulting polyphenylene ether particles were melt kneaded usingan extruder, the polyphenylene ether particles followed the extrudervery well, and it was possible to stably produce a composition. TABLE 1Total 10 min 20 min 40 min 80 min 160 min Amount Average 633 646 683 654635 632 Particle Size μm Fine Particle 0.33 0.39 0.35 0.36 0.34 0.36Rate wt %

Example 2

The same operations as in Example 1 were conducted with the exceptionthat the polyphenylene ether solution (A-2) was used.

For a mixed solution overflowed from the exhaust port, samples werecollected after 10, 20, 40, 80 and 160 minutes from the start ofaddition. During the precipitation, no change was observed in the flowstate of the mixed solution, and it was stable. The average residencetime was 3.3 minutes.

The resulting mixed solution was treated in the same manner as inExample 1, and the weight average particle size of the polyphenyleneether particles and the fine particle rate (the content (wt %) ofparticles having a size of 105 μm or less contained in the polyphenyleneether particles) were measured.

The mixed solution could be filtered without problems.

The volatile matter content of the dried polyphenylene ether particleswas 0.1% by weight or less.

Similarly to Example 1, variations with time of the average particlesize and the fine particle rate of the resulting polyphenylene etherparticles were extremely small, and the fine particle rate thereof wasextremely low.

When the resulting polyphenylene ether particles were melt kneaded usingan extruder, it was possible to stably produce a composition, similarlyto Example 1. TABLE 2 Total 10 min 20 min 40 min 80 min 160 min AmountAverage 503 522 513 515 519 506 Particle Size μm Fine Particle 0.52 0.590.53 0.56 0.54 0.54 Rate wt %

Comparative Example 1

A precipitation tank with a jacket, which had an internal diameter of133 mm and was provided with an exhaust port having a bore diameter of25 mm at a position where the vertical interval between the liquid levelfrom the bottom of the tank and the bottom of the tank corresponded to95 mm, was equipped with no draft tube, and with a one-stage four-bladeinclined paddle blade (inclination: 45 degrees, blade diameter: 33 mm)as a stirring blade.

The volume of a solution remaining in this precipitation tank was 1140ml. In the precipitation tank, 370 g of toluene, 420 g of methanol and10 g of water were placed, and stirred at a stirring revolution of 600rpm. A spiral flow and a vortex occurred all over the inside of theprecipitation tank by stirring.

Hot water was allowed to flow in the jacket to adjust the temperature inthe precipitation tank to 50° C.

Then, the polyphenylene ether solution (A-1) was added at an additionrate of 190 g/minute at a diagonal position to the exhaust port in theprecipitation tank, and a mixed solution of 97.5 wt % of methanol and2.5 wt % of water was added at an addition rate of 100 g/minute from thesame height.

For a mixed solution overflowed from the exhaust port, samples werecollected after 10, 20, 40, 80 and 160 minutes from the start ofaddition. At the start of precipitation, many small-sized particles wereobserved, and the size of the particles gradually increased. Then, fineparticles were produced. Thus, the particle size was not stabilized.

The average residence time was 3.3 minutes.

An attempt was made to treat the resulting mixed solution in the samemanner as in Example 1. However, clogging occurred in filtering, so thatit was necessary to exchange the filter.

The volatile matter content of the polyphenylene ether particles afterdrying was 0.8% by weight.

The weight average particle size of the polyphenylene ether particlesand the fine particle rate (the content (wt %) of particles having asize of 105 μm or less contained in the polyphenylene ether particles)were measured.

Different from the Examples, variations with time of the averageparticle size and the fine particle rate of the resulting polyphenyleneether particles were large, and the fine particle rate thereof was high.

When the resulting polyphenylene ether particles were melt kneaded usingan extruder, the polyphenylene ether particles followed the extruderpoorly, which caused failure in attempting to stably produce acomposition. TABLE 3 Total 10 min 20 min 40 min 80 min 160 min AmountAverage 533 762 453 175 213 401 Particle Size μm Fine Particle 15.6 10.622.4 53.3 48.2 31.2 Rate wt %

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope of the invention.

This application is based on Japanese Patent Application No. 2002-025096filed on Feb. 1, 2002, and the contents thereof are incorporated hereinby reference.

INDUSTRIAL APPLICABILITY

The method of the invention for precipitating polyphenylene ether bymixing a polyphenylene ether solution with a poor solvent forpolyphenylene ether to precipitate polyphenylene ether particles is amethod which can stably produce homogeneous polyphenylene etherparticles with less number of fine particles thereof and reducedperiodic fluctuations in particle size, and which solves the problems indrying the polyphenylene ether particles and in producing apolyphenylene ether resin composition, thus sufficiently complying withthe industrial demands in this field.

1. A method for precipitating polyphenylene ether by mixing apolyphenylene ether solution comprising polyphenylene ether and a goodsolvent therefor with a poor solvent for polyphenylene ether toprecipitate polyphenylene ether particles, the method comprising: usinga precipitation tank equipped with (a) a draft tube, (b) an at leastone-stage stirring blade disposed in the draft tube and selected from aninclined paddle blade, a screw blade and a ribbon blade, (c) one or morebaffles disposed on the outside of the draft tube, (d) a solution supplyport, (e) a poor solvent supply port and (f) an exhaust port; adding, toa mixed solution comprising the good solvent, the poor solvent andpolyphenylene ether particles and circularly flowing by rotation of thestirring blade (b), the polyphenylene ether solution from the solutionsupply port (d) and concurrently a poor solvent from the poor solventsupply port (e), thereby precipitating polyphenylene ether particles;and discharging and recovering the precipitated polyphenylene etherparticles together with the mixed solution from the exhaust port (f). 2.The method for precipitating polyphenylene ether according to claim 1,wherein the mixed solution is overflowed from the exhaust port (f) todischarge the polyphenylene ether particles from the precipitation tank.3. The method for precipitating polyphenylene ether according to claim1, wherein the ratio of the precipitation tank diameter/liquid height ofthe mixed solution in the precipitation tank is from 0.1 to 2, the ratioof the height of the draft tube/said liquid height is from 0.05 to 0.6,and the ratio of a vertical interval between a liquid level and the mostupper portion of the draft tube/said liquid height is from 0.01 to 0.3.4. The method for precipitating polyphenylene ether according to claim1, wherein the good solvent for polyphenylene ether comprises at leastone solvent selected from benzene, toluene and xylene, and the poorsolvent for polyphenylene ether comprises at least one solvent selectedfrom methanol, ethanol, isopropanol, n-butanol, acetone, methyl ethylketone and water.
 5. The method for precipitating polyphenylene etheraccording to claim 1, wherein the weight ratio of the poor solvent/thegood solvent in the mixed solution is from 0.3 to 2.0.
 6. The method forprecipitating polyphenylene ether according to claim 1, wherein the poorsolvent contains water in an amount of 0.3 to 50 parts by weight.
 7. Themethod for precipitating polyphenylene ether according to claim 1,wherein the mixed solution has a temperature of from 30 to 60° C.
 8. Themethod for precipitating polyphenylene ether according to claim 1,giving an average residence time during which the polyphenylene etherparticles stay in the precipitation tank of from 2.0 to 30 minutes. 9.Polyphenylene ether particles obtained by the method according to claim1, having an average particle size of 400 μm or more, and a content offine particles having a particle size of 105 μm or less of 5% by weightor less.